In a motor vehicle comprising a thermal engine and a rotary electrical machine such as an alternator or an alternator-starter, a machine of this type comprises in a non-limiting manner:
a rotor comprising an inductor in which an excitation current is injected; and
a stator comprising a polyphase winding.
In alternator mode, which is also known as generator mode, the machine makes it possible to transform a movement of rotation of the rotor driven by the thermal engine of the vehicle into an electric current induced in the phases of the stator. A rectifier bridge which is connected to the phases of the stator makes it possible to rectify the sinusoidal induced current into a direct current which supplies consumers in the vehicle, as well as a battery.
In particular because of increasing electrification of motor vehicles and development of vehicles of the hybrid type, the requirements for current output in alternator mode on the on-board network of the vehicle are becoming increasingly great. The rotary electrical machine has dimensions to provide a nominal direct current which corresponds substantially to the maximum current which the machine can provide. However, this maximum current is well above the average consumption of current of the motor vehicle. In fact, the motor vehicle does not need a substantial current continually, and the average current provided by the machine is well below the maximum current which it can supply.
A disadvantage of this prior art consists in the fact that the rotary electrical machine is oversized in relation to the average needs of the motor vehicle.
In this context, the objective of the present invention is to eliminate the aforementioned disadvantage.